A semi-automatic image processing method for detecting tag points is already known from a publication by M. Guttman et al. entitled “Tags and Contour Detection in Tagged MR Images of the Left Ventricle” published in IEEE Trans. Med. Imaging, 13:74-88, 1994. This article specifically relates to tag lines. As described in this publication, the user initializes tag line points and these points are followed by an algorithm based on a dynamic programming, which is guided by the user from one image to the next by using an intensity profile. The attribution of a point to a tag line is always checked by the user, because a point could easily be affected to two neighboring tag lines. This method does not use any modeling of tag lines nor any predicted movements of tag lines. According to this known method, the image processing is slow and is consequently difficult to implement in view of diagnosis clinical applications. Moreover, since the algorithm is not fully autonomous for tracking the tag lines, this known method requires many user interactions for yielding a valid tracking of a tag line from one image to the next. Besides, the accuracy of the detection of tag points is not validated by any analysis or reconstruction of movement.